This application is based on Japanese Patent Application No. 2001-341574 filed Nov. 7, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates in general to a sliding device which is disposed between a plurality of members for permitting a smooth movement of the members relative to each other, and a sliding member used for the sliding device.
2. Discussion of the Related Art
As one example of the sliding member, JP-A-60-22080 discloses a swash plate and a shoe of a swash plate type compressor, at least one of which has a solid-lubricant layer including a solid lubricant and a thermosetting resin with which particles of the solid lubricant are held together. Examples of the solid lubricant include molybdenum disulfide, tungsten disulfide, graphite, boron nitride, and fluororesin, while examples of the thermosetting resin include phenol resin, epoxy resin, furan resin, urea resin, polyamideimide resin, and unsaturated polyester. JP-A-8-199327 discloses a swash plate formed of a ferrous material or an aluminum material. The swash plate is covered with a hard layer and a soft layer formed on its surface in this order. The hard layer is formed by spraying of a copper-based or an aluminum-based material, while the soft layer is formed by plating of lead, tin, or lead-tin, or coating of polytetrafluoroethylene, molybdenum disulfide, or molybdenum disulfide-graphite.
Each of the sliding members disclosed in the above-indicated publications has good characteristics. The sliding member, however, is required to be operated under a severer or heavier load conditions, as various devices in which the sliding member is installed are required to have reduced size and weight, and increased performance. Accordingly, there is a demand for developing the sliding member having improved characteristics. As a result of an extensive study made by the inventors of the present invention to meet the demand, it was found that the sliding member having a sliding layer which contains a relatively large amount of polytetrafluoroethylene exhibits excellent resistances to seizure and wear under the heavy load condition in which the swash plate type compressor is operated in a non-lubricating state (dry state), for instance. It is therefore an object of the present invention to provide a sliding device and a sliding member, which exhibit excellent resistances to seizure and wear under the heavy load condition. The object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features of the present invention, for easier understanding of the invention. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A sliding member comprising at least one sliding layer including a solid lubricant and at least one thermosetting resin with which particles of the solid lubricant are held together, the solid lubricant containing 10-40 vol. % of polytetrafluoroethylene.
The sliding member having the sliding layer which contains a relatively large amount of polytetrafluoroethylene exhibits excellent resistances to seizure and wear under a very severe sliding condition or a heavy load condition in which the lubricant is not present or extremely insufficient. Accordingly, the sliding member constructed as described above is suitably used for a sliding device which is operated under the severe sliding condition or heavy load condition. For instance, the present sliding member is used for a sliding device of a compressor, a general-purpose slide bearing, and a sliding portion between a piston and a cylinder block in an engine.
(2) A sliding member according to the above mode (1), wherein the solid lubricant contains not less than 14 vol. % of said polytetrafluoroethylene.
(3) A sliding member according to the above mode (2), wherein the solid lubricant contains not less than 18 vol. % of the polytetrafluoroethylene.
(4) A sliding member according to any one of the above modes (1)-(3), wherein the solid lubricant further contains 5-30 vol. % of molybdenum disulfide.
If the solid lubricant further contains molybdenum disulfide, the sliding member advantageously exhibits further improved sliding characteristics. The molybdenum disulfide is contained in the solid lubricant preferably in an amount of not smaller than 7 vol. %, more preferably in an amount of not smaller than 15 vol. %.
(5) A sliding member according to any one of the above modes (1)-(4), wherein the at least one thermosetting resin contains polyamide imide as a major component.
As the thermosetting resin, it is preferable to employ phenol resin, epoxy resin, furan resin, urea resin, and unsaturated polyester, for example particularly preferably used is polyamide imide resin.
(6) A sliding device comprising:
at least one first sliding member each including at least one sliding layer which includes a solid lubricant and at least one thermosetting resin with which particles of the solid lubricant are held together, the solid lubricant containing 10-40 vol. % of polytetrafluoroethylene; and
at least one second sliding member plated with a nickel-based composition; and
wherein the at least one first sliding member and the at least one second sliding member slide relative to each other.
Where the present sliding member having the sliding layer which contains a relatively large amount of polytetrafluoroethylene slides on a member which is covered with a nickel-based plating, the present sliding member exhibits significantly higher degrees of seizure resistance and wear resistance than the other kind of sliding member which contains a relatively large amount of molybdenum disulfide in place of the polytetrafluoroethylene. Any one of the features according to the above-described modes (2)-(5) is applicable to the sliding device according to this mode (6).
(7) A sliding device according to the above mode (6), wherein the at least one second sliding member includes a base body formed of an aluminum alloy and plated with the nickel-based composition.
(8) A sliding device according to the above mode (6) or (7), wherein the at least one second sliding member is plated by electroless plating of the nickel-based composition.
(9) A sliding device according to any one of the above modes (6)-(8), wherein the at least one second sliding member is plated with at least one nickel-based plating film which is formed of the nickel-based composition and which is selected from a Nixe2x80x94P film, a Nixe2x80x94B film, a Nixe2x80x94Pxe2x80x94Bxe2x80x94W film, and a Nixe2x80x94Pxe2x80x94B film.
(10) A sliding device according to any one of the above modes (6)-(9), wherein the sliding device is used for a compressor.
In the compressor such as a refrigerant gas compressor for an automotive vehicle, the lubricant is mixed in the form of a mist in the pressurized refrigerant gas, so that the sliding member is lubricated by a mist of lubricant contained in the pressurized refrigerant gas. When this type of compressor is re-started after a relatively long period of interruption, the sliding device of the compressor is operated substantially in the absence of the lubricant. In this case, the sliding member tends to suffer from seizure. The sliding member exhibits a higher degree of resistance to seizure with an increase in the amount of the solid lubricant contained in its sliding layer. The increase of the amount of the solid lubricant, however, undesirably lowers the wear resistance of the sliding member. The present sliding member whose sliding layer contains a relatively large amount of polytetrafluoroethylene exhibits high degrees of seizure resistance and wear resistance. The present invention is preferably applicable to sliding devices of various kinds of compressors, e.g., vanes and a rotor or vanes and side plates of a vane compressor, two scrolls of a scroll compressor, shoes and a swash plate of a swash plate type compressor, etc.
(11) A sliding device according to the above mode (10), wherein the compressor is of swash plate type, the sliding device comprising a swash plate as the at least one first sliding member and shoes each as the at least one second sliding member for sliding on the swash plate.
In general, the swash plate is formed of a ferrous material, especially cast iron.
(12) A sliding device according to any one of the above modes (6)-(11), wherein the at least one first sliding member includes a ferrous base body and the at least one sliding layer formed on the ferrous base body.